You are when you eat

The latest fashion in diets is to focus on what time of day you eat. But does it make any difference? Lucie Hoe finds out

You are when you eat is the latest catchphrase among healthy eaters. Instead of obsessing about what's on your plate, a new strategy to stay trim is to focus on what time of day you eat it.

Last week, experts at America's National Institute of Ageing suggested that consuming meals only between 4pm and 7pm, as our hunter-gatherer ancestors did, is a successful way to lose weight and keep it off.

Here is a guide to some of the healthy and not-so-healthy clock-watching approaches to eating.

Eat all you can between four and seven o'clock

Advocates: Dr Mark Mattson, chief of the laboratory of neurosciences at America's National Institute of Ageing.

The so-called warrior diet mirrors the eating habits of our cave-dwelling ancestors who consumed their daily intake between 4pm and 7pm, when, Mattson says, we "are at our hungriest".

"Our basic metabolism was set up when we were hunter-gatherers," he says. "The pattern would have been a mixture of feast and famine. We not only get much less exercise than our distant ancestors, but having a regular food supply as opposed to an intermittent one may prove to be almost as damaging."

Frankie Phillips, a spokesman for the British Dietetic Association, disagrees. "It is impractical and quite unrealistic to think people could adopt this approach today," she says. "Avoiding food until 4pm leaves you prone to unhealthy snacking out of hunger. And plenty of studies have shown that if you are well-nourished and eat regularly throughout the day, it has benefits for mental performance, as well as the waistline."

A carb curfew after 5pm

Nutritionist Joanna Hall says the approach creates a "calorie gap" between the number of calories consumed and the number burned off by banning carbohydrates in the evening. In addition, eating more protein will help you to stay fuller for longer, she says. "Evenings are the time when most people munch on high-fat foods, such as cakes and biscuits, because they are bored or tired," says Louise Sutton, a senior lecturer in health and exercise science at Leeds Metropolitan University. "So this is one way of stopping that."

Experts are sceptical, as there is no scientific evidence to support the claims, but agree that if it helps to reduce night-time nibbles, it is a good thing.

Three square meals a day

Advocates: our grandparents.

It may be rare today, but three cooked meals a day was pretty much the only approach to eating in the 1940s and earlier, says Helen Andrews, a nutrition scientist at the British Nutrition Foundation.

"All meals were substantial and the average calorie intake was higher than it is today, but people were much more active," Andrews says. "Very few people would skip breakfast, lunch or dinner and snacking between meals was unheard of. There is nothing wrong with this approach, other than it is simply not practical for most modern lifestyles."

Eat your main meal after 9pm

Advocates: the Spanish, the French and the Italians.

This is not a faddish diet, but a lifestyle habit. Evening meals, the main meal of the day, are often eaten much later than 9pm in Spain, which is one reason why snacking in tapas bars is so popular - -as a means as staving off hunger as much as anything else. However, Sutton says the approach is not recommended unless you are used to it. "Going to bed on a full stomach can raise the risk of indigestion and heartburn," she says. "It doesn't suit everyone."

Fast before noon

Advocates: Claudia Schiffer.

Eating very little before midday is the way Schiffer maintains her supermodel shape. "I keep my daily calorie count down by eating nothing but fruit and vegetables before noon," she says.

Skipping breakfast is a growing trend in Britain. A report by the World Health Organisation showed that around 60 per cent of girls and 66 per cent of boys in the UK no longer eat morning meals. But is it healthy?

"Definitely not," says Sutton. "Eating fruit in the morning, like Claudia Schiffer, is fine, but countless studies show if you eat nothing, you will make up for it by consuming more high-calorie foods later."

Eat every three hours

Advocates: leading American personal trainer Jorge Cruise, author of The 3-Hour Diet.

Cruise believes that eating at three-hour intervals "stimulates the body to lose weight", whereas spacing out meals any more "sends the body into starvation mode and forces it to cling to stored fat".

Following the same principles is the UK's Vitaline diet, which recommends eating a small meal every three hours, but snacking on a tiny piece of protein or a nibble of carbohydrates every 13 minutes to boost the metabolism.

While the strict timings of these approaches are questionable, there is evidence that eating mini-meals is healthy. Professor Andrew Prentice of the Medical Research Council's international nutrition group says little and often is a good approach to eating. "Metabolically, it looks as though regular nibbling is a good way to do things," he says.

"It puts less strain on the body if you are not taking in too much food all at once."

Breakfast like a king

Advocates: leading nutritionists and scientists.

Breakfast kick-starts your metabolism, which becomes sluggish overnight, so it should be the most important meal of the day. There is plenty of scientific research to back up this claim. This month, researchers at the Maryland Medical Research Institute found that girls who ate a low-fat, high-fibre breakfast cereal were slimmer than those who skipped the morning meal. Other studies have shown that breakfast cereal eaters snack less on highly calorific foods throughout the day.

"Not eating breakfast is really the worst thing you can do," says Bruce Barton, the nutrition scientist who headed the Maryland study.

Eat one day, starve the next

Advocates: a growing body of scientists.

"Intermittent feeding schedules", which lead to the consumption of one third less calories overall, have long been shown to increase the health and lifespan of rats. Now, experts are beginning to think the approach might be beneficial for humans. American studies by Dr Mattson and his colleagues at the National Institute of Ageing showed that animals who were made to fast for a day but allowed to eat as much as they wanted the next not only lost weight, but had improved blood pressure and markers for diabetes.

However, Dr James Stubbs, of the Rowett Research Institute in Aberdeen, says: "Even if intermittent feeding did promote weight loss to begin with, the body would adapt and weight would soon go up again."

The right food at the right time

Chronobiologists at the University of Cambridge have studied the body's circadian rhythms and identified ideal time slots for eating and exercising.

7-8am Eat breakfast

It is best to eat after some light, early-morning stretching or yoga.

10am Have a snack

The body uses 20 per cent of the brain's available glucose by around this time, so a low-fat carbohydrate snack, such as a banana, bagel or sports energy bar, is needed to top up levels.

1pm Eat lunch

Energy levels are naturally running low at this time. Leave it any later and you are more likely to consume a greater number of calories.

2-3pm Have a snack

Glucose levels plummet in a post-lunch dip. Some cashew nuts, plain popcorn, or dried or fresh fruit will get you back on track.

4-6pm Do a workout

Muscle temperature and other fitness parameters reach a peak around now.

5-7pm Eat an evening meal

After this time, we tend to need more food to feel full. Eating now also allows time for food to be fully digested before going to bed.

7-9pm Eat a bedtime snack

Choose cottage cheese, a slice of turkey or a banana, all of which contain tryptophan, a substance that is a precursor to a good night's sleep.